Double split in C

Question

OK. For example I have this line in my txt file:

1|1,12;7,19;6,4;8,19;2,2
As you can see, it has 2 parts, separated by |. I have no problems getting both parts, and separating second part 1,12;7,19;6,4;8,19;2,2 using ; separator. BUT I do have problems with separating further by , to get first and second number of each set.

This is my current code:

  result = strtok(result, ";");

  while(result != NULL ) {
      printf("%s\n", result);
      result = strtok(NULL, ";");
  }

It outputs me:

1,12
7,19
6,4
8,19
2,2

OK, great. But when I try to 'strtok' (I'm using this method for splitting) like this:

 result = strtok(result, ";");

 while(result != NULL ) {
     //printf("%s\n", result);
     help    = strtok(result, ",");    
     while(help != NULL) {
         printf("<%s>", help);
         help = strtok(NULL, ",");
     }

     result  = strtok(NULL, ";");
 }

I only get "<1>,<12>" like there is only one set in this set of numbers. I dont understand where are the rest of the numbers. Instead, output should be: <1>,<12>,<7>,<19>,<6>,<4>,<8>,<19>,<2>,<2>. Could someone please give a solution, how to get EACH number of each set this set of numbers. Maybe there are other methods or I'm doing something wrong :)

Thank you!

Answer 1

In addition to what Neil pointed out regarding modifying the original string, the strtok() function is not designed to be used in a nested manner like you describe. You may wish to investigate the strtok_r() function, or avoid the use of the strtok* family altogether.

Answer 2

char *strtok(char *str, const char *delim); (from man pages)
The delim argument specifies a set of characters that delimit the tokens in the parsed string. The caller may specify different strings in delim in successive calls that parse the same string.

So, use both ; and , as delimiter to get all the numbers.

//this will delimit result whenever ";" or "," is found
result = strtok(result, ";,"); 

while(result != NULL ) {
    printf("%s\n", result);
    result = strtok(NULL, ";,");
}

Answer 3

As others have pointed out, strtok() isn't reentrant - it maintains internal state about the string it's parsing, so it can't be used to parse two different strings simultaneously (which means two different non-NULL values for its first argument, so your situation counts).

If you have the reentrant version strtok_r() available, you can change your code to use it like so:

char *st_result, *st_help;
result = strtok_r(result, ";", &st_result);

while (result) {
     printf("[%s]", result);
     help = strtok_r(result, ",", &st_help);    
     while (help) {
         printf("<%s>", help);
         help = strtok_r(NULL, ",", &st_help);
     }

     result = strtok_r(NULL, ";", &st_result);
}